Roll control system for flexible wing aircraft



Feb. 28, 1967 P. F. GIRARD 3,366,559.

ROLL CONTROL SYSTEM FOR FLEXIBLE WING AIRCRAFT Filed Nov. 4, 1963 2Sheets-Sheet 1 I N VENTOR.

PETER F. GIRARD BY V ..AM -W 14241012 8; 5444735 P. F. GIRARD 3,305,559

ROLL CONTROL SYSTEM FOR FLEXIBLE WING AIRCRAFT Feb. 28, 1967 2Sheets-Sheet 2 Filed Nov. 4, 1963 INVENTOR. PETER F. GIRARD mm on E 3United States Patent 3,306,559 ROLL CONTROL SYSTEM FOR FLEXIBLE WINGAIRCRAFT Peter F. Girard, La Mesa, Calif., assignor to The RyanAeronautical Co., San Diego, Calif. Filed Nov. 4, 1963, Ser. No. 320,9956 Claims. (Cl. 24490) The present invention rel-ates to aircraft andmore specifically to a roll control system for flexible wing aircraft.

The flexible wing type aircraft with a payload suspended below the wingis inherently very stable and directional control is usually obtained byshifting the center of gravity of the payload relative to the center oflift of the wing. With the payload pivotally suspended from the wing,the center of gravity is shifted by swinging the payload. Due to thependulum stability characteristics this results in the wing beingtilted, the change in effective lift vector causing the directionalchange in flight. With heavy payloads the control forces required toprovide the control action are considerably more than those required tooperate conventional aircraft controls and it is desirable to minimizethese forces.

The primary object of this invention, therefore, is to provide a rollcontrol system wherein small portions of the flexible wing are madecontrollable, causing an aerodynamic unbalance which results in orassists the directional control of the aircraft.

Another object of this invention is to provide a control system whereinthe initial control action actuates the small portions of the wing,continued control action causing tilting of the entire wing, using asingle mechanism.

Another object of this invention is to provide a control system whereinthe wing pivotal axis for roll motion is disposed in such a positionthat rolling action of the wing does not change the direction of freestream air flow over the wing.

A further object of this invention is to provide a control system whichis adapted to a variety of sizes and configurations of flexible wingaircraft, with manual, automatic, or remote control.

In the drawings:

FIGURE 1 is a top plan view of the Wing, portions being cut away to showthe control system;

FIGURE 2 is a side elevation view of the aircraft;

FIGURE 3 is an enlarged side elevation view of the wing to payloadpivotal joint;

FIGURE 4 is an enlarged sectional view taken on line 44 of FIGURE 2; and

FIGURE 5 is a further enlarged view of a portion of the control system,as taken from the rear of FIGURE 4.

Similar characters of reference indicate similar or identical elementsand portions throughout the specification and throughout the views ofthe drawing.

General structure The wing has a rigid longitudinal keel 12, from theforward end of which a pair of leading edge members 14 extend rearwardlyon opposite sides and secured between the keel and leading edge membersare flexible lifting panels 16 and 18. The leading edge members 14 areheld apart in a V form, divergent from the forward end, by a transversespreader bar 20 passing below the keel 12 and being attached to saidleading edge members by hinge brackets 22 having their pivotal axesparallel to the vand a corresponding decrease in lift.

3,306,559 Patented Feb. 28, 1967 spreader .bar. Keel 12 has a yoke 24which is pivotally attached to brackets 26 on spreader bar 20 to pivotabout an axis substantial-1y co-axial with hinge brackets 22.

Fixed to the center of spreader bar 20 is a roll hinge pin 28 extendinglongitudinally of the aircraft and being journalled in a mounting 30,from which a payload 32 is suspended on a suitable frame 34. The axis ofroll hinge pin 28 is substantially parallel to the normal line of flightof the aircraft, or the longitudinal axis thereof, rather than beingparallel to keel 12, which is at the high angle of attack peculiar toflexible wing aircraft, as indicated in FIGURES 2 and 3.

Control system The leading edge members 14 have hinged tip port-ions 36and 38 forming the rear ends thereof, the hinges 40 being disposed sothat the ti portions swing in planes substantially parallel to theplanes of the lifting panels 16 and 18 at their lines of attachment tothe hinged portions. In other words the hinge axis of each hinge isperpendic ular to the plane of the flexible lifting panel where it issecured to the leading edge member. At the hinged ends of tip portions36 and 38 are control arms 42 and 44 to which are attached controlcables 46 and 48, said control cables passing around pulleys 50 andextending inwardly. Below the keel 12 the control cables 46 and 48 crossand are secured together by a connector 52 for differential action, thecables then continuing to pulleys 54 attached to spreader bar 20 andextending downwardly therefrom to an actuator 56. Pulleys 54 aredisposed between the center and ends of spreader bar 20, equally spacedon opposite sides of hinge pin 28. At the pulleys 54 are brackets 58having stop portions 60 through which control cables 46 and 48 pass,said cables each having a stop collar 62 fixed thereon to engage therespective stop portion and limit movement of the cable.

Actuator 56 is illustrated in FIGURE 4 as a rocker arm with the controlcables attached to opposite ends thereof, a jack 64 being coupled to theactuator for rocking motion. The arrangement is similar to that ofconventional aircraft ailerons and the control can be manual, or poweroperated by remote or automatic means, the specific actuating system notbeing critical.

Operation In normal flight the Wing is stable and maintains a particularflight path. When roll control is applied, as indicated in broken linein FIGURE 4, the actuator 56 pulls one control cable down, in this casethe cable 46, and allows the other cable 48 to rise. Since the cablesare secured together at their cross over by connector 52, the properproportion of differential motion is maintained. Control cable 46 pullson arm 42 causing tip portion 36 to swing outwardly and downwardly, solowering the profile of trailing edge of the wing panel 16 andeflectively increasing its angle of attack, resulting in increased lifton that panel. Simultaneously, the slackening of control cable 48 allowstip portion 38 to swing inwardly andupwardly, pulled by the areodynamicpressure on lifting panel 18. This raises the profile of the trailingedge of panel 18, causing a decrease in effective angle of attack Theoffset in lift causes a rolling action to the left, as viewed in FIGURE4. The axes of hinges 40 are not particularly critical, but the swingingof the tip portions in the planes defined above causes less distortionof the lifting panel shape .than a mere lateral or vertical motion ofthe tips.

Motion of the control cables is, however, limited by the stop collars 62against stops 60. Thus only the initial motion of the actuator 56 movesthe tip portions 36 and 38 in the manner of ailerons to initiate therolling action. Continued movement of the actuator with the controlcable 48 held by stop collar 62, as in FIGURE 5, will result in thespreader bar 20 being tilted about roll hinge pin 28. In FIGURE 5 theoffset position is indicated in full line, with the neutral position inbroken line. The spreader bar 20 carries the entire wing to the tiltedposition, the resultant change in total lift vector causing the requiredroll or turning action.

Without the movable tip portions all roll control would be obtained bymoving the entire wing, which would require considerable actuatingforce. By means of the movable tips, a small actuating force is used toinitiate a roll motion, greatly decreasing the total force required.Small roll motions, such as corrective motions in normal flight, can beobtained entirely with the movable tips, without moving the completewing, the degree of control depending on the range of movement designedinto the tip portions. It would be feasible, therefore, to eliminate theroll hinge pin 28 and use the tip portions only for control, dependingon the required performance of the aircraft.

As illustrated, however, the roll hinge pin 28 is parallel to thelongitudinal axis of the aircraft, or generally parallel to the normalline of flight. If the hinge axis were parallel to the keel 12,inclination of the wing about that axis would change the direction offree stream air flow over the wing. This action would introduce a yawangle between the wing and relative air flow which, in the flexiblewing, results in a rolling moment opposed to the applied roll, soincreasing control force. By making the hinge axis parallel to the lineof flight, the relative air flow over the wing will be subjected tolittle if any change at any position of the wing about the roll hingeaxis. The control force is thus not increased by yaw effect as the wingis inclined.

The system is particularly suitable for piloted aircraft having manualcontrol, since the physical effort required for control is minimized. Inunmanned aircraft the size of the servo mechanisms and their powerrequirements can be reduced, resulting in an increase in useful payload.

It is understood that minor variation from the form of the inventiondisclosed herein may be made without departure from the spirit and scopeof the invention, and that the specification and drawings are to beconsidered as merely illustrative rather than limiting.

I claim:

1. In an aircraft:

a wing having a rigid longitudinal keel, leading edge members divergingrearwardly from the forward end of said keel, flexible lifting panelssecured to and extending between said keel and said leading edgemembers, and spreader means secured to and holding said leading edgemembers in spaced relation;

the rear tip portions of said leading edge members being hinged;

and control means operatively connected to said tip portions to move thesame differentially.

2. In an aircraft:

a wing having a rigid longitudinal keel, leading edge members divergingrearwardly from the forward end of said keel, flexible lifting panelssecured to and extending between said keel and said leading edgemembers, and spreader means secured to and holding said leading edgemembers in spaced relation;

the rear tip portions of said leading edge members being hinged to swingin planes substantially parallel to the respective lifting panels attheir attachments to the leading edge members;

and control means operatively connected to said tip portions to swingthe same differentially.

3. In an aircraft:

a wing having a rigid longitudinal keel, leading edge members divergingrearwardly from the forward end of said keel, flexible lifting panelssecured to and extending between said keel and said leading edgemembers, and spreader means secured to and holding said leading edgemembers in spaced relation;

a frame adapted to carry a payload;

said wing being pivotally attached to said frame to swing about an axissubstantially parallel to the longitudinal axis of the aircraft with thewing at a positive angle of attack relative thereto;

the rear tip portions of said leading edge members being hinged to swingin planes substantially parallel to the respective lifting panels attheir attachments to the leading edge members;

and control means operatively connected to said tip portions to move thesame differentially.

4. In an aircraft:

a wing having a rigid longitudinal keel, leading edge members divergingrearwardly from the forward end of said keel, flexible lifting panelssecured to and extending between said keel and said leading edgemembers, and spreader means secured to and holding said leading edgemembers in spaced relation;

a frame adapted to carry a payload;

said wing being pivotally attached to said frame to swing about an axissubstantially parallel to the longitudinal axis of the aircraft with thewing at a positive angle of attack relative thereto;

said leading edge members having integral rear tip portions pivotallyattached thereto;

control elements operatively connected to said tip portions to move thesame differentially.

stop means on said control elements to limit the movement of said tipportions;

and stops on said wing engageable with said stop means, wherebycontinued motion of said control elements beyond the stop engagedposition causes pivoting of the entire wing relative to said frame.

5. In an aircraft:

a wing having a rigid longitudinal keel, leading edge members divergingrearwardly from the forward end of said keel, flexible lifting panelssecured to and extending between said keel and said leading edgemembers, and spreader means secured to and holding said leading edgemembers in spaced relation;

a frame adapted to carry a payload;

said Wing being pivotally attached to said frame to swing about an axissubstantially parallel to the longitudinal axis of the aircraft with thewing at a positive angle of attack relative thereto;

the rear tip portions of said leading edge members being hinged to swingin planes substantially parallel to the respective lifting panels attheir attachments to the leading edge members;

control cables connected to said tip portions;

said control cables crossing and being secured together adjacent saidkeel;

said spreader means comprising a spreader bar with 1pullleys mountedthereon on opposite sides of said said cables passing around saidpulleys;

and an actuator connected to the ends of said cablesfor differentialmovement thereof.

6. In an aircraft;

a wing having a rigid longitudinal keel, leading edge members divergingrearwardly from the forward end of said keel, flexible lifting panelssecured to and extending between said keel and said leading edgemembers, and spreader means secured to and holding said leading edgemembers in spaced relation;

a frame adapted to carry a payload;

said wing being pivotally attached to said frame to swing about an axissubstantially parallel to the longitudinal axis of the aircraft with thewing at a positive angle of attack relative thereto;

said leading edge members having integral rear tip portions pivotallyattached thereto;

control'cables connected to said tip portions;

said control cables crossing and being secured together adjacent saidkeel;

said spreader means comprising a spreader bar with pulleys mountedthereon on opposite sides of said keel;

said cables passing around said pulleys;

an actuator connected to the ends of said cables for difierentialmovement thereof;

stops adjacent said pulleys;

and stop means on said cables engageable with said 15 stops to limitmovement of said tip portions, whereby movement of said actuator beyondthe stop engaged 6 position causes pivotal motion of the entire wingrelative to said frame.

References Cited by the Examiner UNITED STATES PATENTS 6/ 1964 Girard244-138 X OTHER REFERENCES NASA Technical Note NASA TN D-1946 Full-Scale10 Wind-Tunnel Investigation of a Flexible-Wing Manned Test Vehicle, byJ. L. Johnson, Jr., and J. L. Hassell Jr., pages 5, 15, 16, 29, 21,August 1963.

MILTON BUCHLER, Primary Examiner.

FERGUS S. MIDDLETON, Examiner.

A. E. CORRIGAN, Assistant Examiner.

1. IN AN AIRCRAFT: A WING HAVING A RIGID LONGITUDINAL KEEL, LEADING EDGEMEMBERS DIVERGING REARWARDLY FROM THE FORWARD END OF SAID KEEL, FLEXIBLELIFTING PANELS SECURED TO AND EXTENDING BETWEEN SAID KEEL AND SAIDLEADING EDGE MEMBERS, AND SPREADER MEANS SECURED TO AND HOLDING SAIDLEADING EDGE MEMBERS IN SPACED RELATION; THE REAR TIP PORTIONS OF SAIDLEADING EDGE MEMBERS BEING HINGED; AND CONTROL MEANS OPERATIVELYCONNECTED TO SAID TIP PORTIONS TO MOVE THE SAME DIFFERENTIALLY.